Pilot-signal for telephone-switchboards.



No. 650,486. Patented May 29, I900. c. E. scmsuan.

PILOT SIGNAL FOB TELEPHONE SWITCHBOARDS.

(Application filed June 17, 1898.)

(N o I o d e I.)

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7 UNITED STATES PATENT ()FFICEQ CHARLES E. SCRIBNER, or CHICAGO,ILLINOIS, Assienon TO THE WESTERN ELECTRIC COMPANY, or SAME PLACE;

PILOT-SIGNAL FOR TELEPHONE-SWITCHBIOARDS'.

srncrrrcn'rron forming part of Letters Patent No. 650,486, dated m 29,1960.

Application filed June 17,1898. Serial No. 683;?41. (NomodeL) To allwhom it may concern;

Be it known that I, CHARLES E. SoRIB'NER', a citizen of the UnitedStates, residing at Ohicago, in the county of Cook and State ofIllinois, have invented a certain new and useful Improvement inPilot-Signals for Telephone- Switchboards, (Case No. 460,) of which thefollowing is a full, clear, concise, and exact description.

This invention concerns general or pilot signals for association withgroups of individual line-signals in telephone-switchboards. It appliesparticularly to telephone-lines provided with means for producing acurrent in the line when the telephone is taken for use, together withline-signals in the switchboard responsive to such currents.

Prior to this invention a relay has been provided, in a circuit commonto all the individual line-signals, with a winding of high resistanceand a winding of low resistance, together with switch-contacts forbringing the low-resistance winding into action when the relay is madeoperative and with other switchcontacts and a local circuit controlledthereby containing the pilot or general signal. This appliance has beenfound defective, however, in that the two pairs of switch-contacts ofthe relay are difficult of adjustment and uncertain of operation. Thepresent invention is an improvement on this appliance. It consists incombining with the relay having two windings, one permanently in thecircuit common to the different line-signals and the other normallyopen, a local circuit containing the pilot-signal controlled by a singlepairof switch-contacts actuated bythe said relay, and a second relayhaving a single pair of switch-contacts controlling the connection ofthe normally-open winding of the first-mentioned relay with the circuit,the magnet of said last-mentioned relay being in the local circuitreferred to. Thus the two pairs of switch-contacts actuated by the samerelay are replaced by switch-contacts of separate relays, each of whichis simple of adj ustment and reliable in operation.

The invention is illustrated diagrammatically in the attached drawing,which represents a group of three telephone-lines each provided with asecondary line-signal and with means for controlling the line-signalautomatically in the use of the telephone,a pilotsignal and mechanism inaccordance with the present invention being shown in association 5 withthe group of lines. Each line-circuit is normally open at its substationas respects continuous currents. At the station the telephone-circuitsand the controlling switch thereof are arranged to 60. complete theline-circuit when the receivingtelephone is removed from its switch foruse. Each line is equipped at the central office with the usualspring-jack for making connection with it, with a relay responsive toourrent in the line determined in the use of the telephone and asecondary signal controlled by the relay, the line-circuits being led tothe poles of a battery common to the difierent lines to serve as asource of current for op- 7o crating the signals. Thus line conductors 1and 2 to station A are connected with springjack 1), being normallycontinuous through the switch-contacts of the spring-jack. Extensions ofthese line conductors lead to earth and to one pole of the commonbatteryc, respectively, the magnet-winding of a relay d being includedin line conductor 2. This relay controls the continuity of a localcircuit made up of conductors 3 and 4, the latter of which includes asecondary signal e, which is associated with the spring-jack of the linein the switchboard. The former conductor is common to the differentlines of the group and extends to the free pole of the grounded battery0. In applying the present invention to such a group of telephone-linesa winding h of a relay h is interposed in the common conductor 3 of thelocal signal-circuits. This winding should preferably be of comparaotively-high resistance, five ohms being sufiicient. The. switch-contactsh 7L4 of relay 72. control the continuity of a local circuit 5 6, whichincludes the pilot-lamp or general signal '5. Conductor 5 leads from thecontact lever 71. of the relay to the battery 0, while the otherconductor 6is connected with earth through the pilot signal 2'. Themagnetwinding of a second relay Z is interposed in a branch 7 ofconductor 6 in multiple with the loo pilot-signal. The switch-contacts ZZ of this relay control the continuity of a wire 8, which includes awinding 72. of the relay h., This winding should be of very lowresistance, onestantly attract the attention of the operator.

The removal of a telephone at any station of the group from its switchpermits the battery c to create acurrent in the line, which excites thecorresponding relay'd and thus effects the closure of the local circuitcontrolled by that relay. The closing of this local circuit permitscurrent to flow from battery through conductors 3 and 4. This currentmay be lllSllffiClGIl'O to illuminate the-signal e of the line, but willexcite the high-resistance winding of magnet 71. and will thus bringabout the closure of the local circuit 5 6. The closure of the localcircuit 5 6 causes the display of the pilot-signal vland simultaneouslybrings about the excitement of the relay Z, which,'closing itscontact-points, completes the branch 8 through the low-resistancewinding ]L2 of relay h. Now sufficient current flows in the circuit 34to light the secondary line-signal e of the calling line. If the currentin the calling line be now interrupted, the current through the circuit3 4 will be broken at the line-relay d, whereupon the relay It willbecome inert and will permit the extinction of signal t' and thedemagnetization of relay Z.

I claim asthe invention- The combination with telephone-lines and meansfor producing current in the lines in the use of the telephones, aline-relay for each line responsive to such current, a local circuitcontrolled by each relay, and a secondary line-signal therein, of arelay having a high-resistance winding in a conductor common to saidlocal circuits, a second local cir cuit and a pilot-signal includedtherein controlled by said relay, a low-resistance wind- 1 ing of thesaid relay connected with the local circuit of the secondary signals,and a relay in the local circuit with the pilot-signal controlling thecontinuity of the circuit through said low-resistance Winding,substantially asdescribed.

In witness whereof I hereunto subscribe my name this 31st day ofJanuary, A. D. 1898.

CHARLES E. SGRIBNER. \Vitnesses:

ELLA EDLER, MYRTA F. GREEN;

